The two categories of forces are referred to as internal forces and external forces.For our purposes, we will simply say that external forcesinclude the applied force, normal force, tension force, friction force, and air resistance force. And for our purposes, the internal forces include the gravity forces, magnetic force, electrical force, and spring force. When net work is done upon an object by an external force, the total mechanical energy (KE + PE) of that object is changed. If the work is positive work, then the object will gain energy. If the work is negative work, then the object will lose energy. The gain or loss in energy can be in the form of potential energy, kinetic energy, or both. Under such circumstances, the work that is done will be equal to the change in mechanical energy of the object. Because external forces are capable of changing the total mechanical energy of an object, they are sometimes referred to as nonconservative forces. When the only type of force doing net work upon an object is an internal force (for example, gravitational and spring forces), the total mechanical energy (KE + PE) of that object remains constant. When the only forces doing work are internal forces, energy changes forms - from kinetic to potential (or vice versa); yet the total amount of mechanical is conserved. Because internal forces are capable of changing the form of energy without changing the total amount of mechanical energy, they are sometimes referred to as conservative forces. When work is done by external forces (nonconservative forces), the total mechanical energy of the object is altered.
Electricity Bill Assignment Objective Estimate how much electrical energy you consume on a daily basis (ie: what does it cost my parents)
What to do?
Identify 10 electrical appliances you use on a daily basis and identify their power rating (in Watts).
Iphone charger- 10 watts
Fridge- 725 watts
Water cooler- 960 watts
Microwave- 1450 watts
Hair dryer- 1875 watts
Toaster oven- 1400 watts
Clock radio- 10 watts
Desktop computer- 250 watts
Flat iron- 20 watts
Laptop charger 438 watts
The power rating will be listed on the info label – typically on the back of or under the appliance. Often the power consumption is listed in terms of AMPERAGE (amperage measures the current of electricity consumed). The power rating (in Watts) may be calculated using the following formula:
Power (in Watts) = AMPS x 120 volts.
For example, a 12 AMP vacuum cleaner uses 12A x 120v = 1440 Watts of power.
Determine the total kWh (kilowatt-hours) of power that you consume with these ten appliances.
First estimate how many hours you use each appliance. For example, you may use your hairdryer every second day for 10 minutes – so on average you use it for 0.17h/d ¸ 2 = 0.085 h per day.
Calculate the kWh used per day by multiplying the wattage of the appliance by the hours used (per day).
Finally, determine the total kWh you use per day.
53.5229
What does this cost your parents?
$3.75
Look at your household electric bill. Find two numbers:
the total dollar amount due = $318.93
kWh consumed that month = 1714 kWh
Costs of Electricity.
Calculate the average cost per kWh by dividing the dollar amount by the kWh consumed. This is approximately what each kWh costs your family. (Note: this figure includes fees and taxes, too). The cost will probably be between $0.10-$0.20 per kWh – depending on how much electricity you use. Electricity costs more if you exceed a certain usage.
$0.19
$0.12
They are different because there are many costs that the electric company incorporates which aren’t part of specifically only the kilowatts used.
You can also look this value up on the bill itself.
Compare the two values. Why are they different?
Multiply the kWh you use per day by the cost per kWh to determine what you cost your parents.
$10.17
Evaluate
Does the cost of electricity seem like a lot to you? Discuss this with your friends.
It seems like a lot of money to use per day. I definitely need to change the amount that I use, although many of the appliances that I used were large and need a lot of power, like the refridgerator.
Keep in mind that this cost only reflects ten appliances. What do you think your total cost actually is? Are there major appliances that you may have excluded from your list of ten that would make a big difference?
I think I included all of the main items.
If you think your consumption is a lot – what can you change? Do you need/should change?
I need to make sure to shut of more items during the day when I’m not actually using them.
I think that the cost of energy is very expensive. And considering that my personal cost is considerably high, I should definitely look for ways to reduce it. I didn't really realize that even when I keep things plugged in at my house, energy is being spent still, plugged in to an appliance or not. Therefore, I need to make it a habit to unplug everything whenever I'm not using it.
The Work-Energy Relationship 1/30
The two categories of forces are referred to as internal forces and external forces.For our purposes, we will simply say that external forcesinclude the applied force, normal force, tension force, friction force, and air resistance force. And for our purposes, the internal forces include the gravity forces, magnetic force, electrical force, and spring force. When net work is done upon an object by an external force, the total mechanical energy (KE + PE) of that object is changed. If the work is positive work, then the object will gain energy. If the work is negative work, then the object will lose energy. The gain or loss in energy can be in the form of potential energy, kinetic energy, or both. Under such circumstances, the work that is done will be equal to the change in mechanical energy of the object. Because external forces are capable of changing the total mechanical energy of an object, they are sometimes referred to as nonconservative forces.When the only type of force doing net work upon an object is an internal force (for example, gravitational and spring forces), the total mechanical energy (KE + PE) of that object remains constant. When the only forces doing work are internal forces, energy changes forms - from kinetic to potential (or vice versa); yet the total amount of mechanical is conserved. Because internal forces are capable of changing the form of energy without changing the total amount of mechanical energy, they are sometimes referred to as conservative forces. When work is done by external forces (nonconservative forces), the total mechanical energy of the object is altered.
Electricity Bill Assignment
Objective
Estimate how much electrical energy you consume on a daily basis (ie: what does it cost my parents)
What to do?
- The power rating will be listed on the info label – typically on the back of or under the appliance. Often the power consumption is listed in terms of AMPERAGE (amperage measures the current of electricity consumed). The power rating (in Watts) may be calculated using the following formula:
Power (in Watts) = AMPS x 120 volts.For example, a 12 AMP vacuum cleaner uses 12A x 120v = 1440 Watts of power.
- What does this cost your parents?
$3.75Evaluate
I think that the cost of energy is very expensive. And considering that my personal cost is considerably high, I should definitely look for ways to reduce it. I didn't really realize that even when I keep things plugged in at my house, energy is being spent still, plugged in to an appliance or not. Therefore, I need to make it a habit to unplug everything whenever I'm not using it.